The present invention relates to the dispensing of flexible sheet material, such as toilet tissue, paper toweling, or the like, from rolls. More particularly, the invention relates to apparatus for applying a braking force to the rolls as they rotate in a dispenser in order to prevent the occurrence of undue overspin during the dispensing operation.
Flexible sheet material of the concerned type is characteristically dispensed from a rotatable core about which the material is wound. Dispensing of the material is generally effected by the core being mounted for rotation via trunnions and the core rotated by pulling on the leading end of the web of sheet material that is wound about the core. Dispensers currently in use, such as that described in U.S. Pat. No. 3,739,965 to P. W. Jespersen, et al. and assigned to the assignee herein, commonly employ mechanisms such as time-stops, sheet cut-off devices and/or automatic web feeding mechanisms that add to the energy required to pull the sheet material web from the dispenser. In order to avoid the problem of causing the sheet material, when wet, to simply break off in the user's hands due to the presence of excessive drag on the core, it is desirable to keep such drag to a minimum, as for example, by the use of low-friction journalling means.
A problem arises, however, in instances where the core is journalled in low-friction bearings, that problem being the occurrence of overspin on the body of sheet material when the user imparts excessive pull on the leading end of the web. Overspin, as is well known, is capable of producing a mass of loose material that is released from the wound body and that can reach proportions at which the dispenser can become jammed and thereby rendered inoperative.
The use of braking apparatus in sheet material dispensers of the concerned type is not new, such apparatus being described in U.S. Pat. Nos. 2,699,903, 3,770,221, 4,447,015 and 4,660,781. Braking apparatus which consist essentially of spring-loaded flaps on the roll surface, or spring devices to effect end pressure are not totally dispositive of the problem of concern, however, in that they not only add to the number of mechanisms and components required by the dispenser thereby adding to the space requirement of the dispensers, their cost and their propensity to fail, but they also suffer the disadvantage that, being essentially inertia-dependent, as the weight of the roll decreases so also is the ability of the braking apparatus to control overspin reduced.
Commonly in prior art sheet material dispensing devices of the type in which the inertia and spin of the roll is proportional to the weight of the roll and not its diameter, the braking effect must be compromised by requiring its reduction as the weight of the roll decreases. Thus, in the design of such devices, if the braking characteristics are designed to be accurately effective when the roll acquires a small diameter, then it will concomitantly be of reduced effect when the roll is full, thereby resulting in the undesired overspin. Conversely, if the braking effect is designed to be accurate when the roll is substantially full then, at a near empty condition, the roll will be difficult to rotate thereby resulting in the possible undesired tearing of chips of paper.
It is to the amelioration of these problems therefore, to which the present invention is directed.